Topband: Inverted ELL for 160M
Jerry Keller
k3bz at arrl.net
Wed Nov 3 14:09:13 EST 2004
Many thanks to those who responded to my question with some good comments and ideas. Almost everyone
said I should use radials on the ground rather than elevated, but I think I have to stick with the
two elevated radials to start with due to physical constraints onsite. But I'll keep the advice in
mind and try to figure a way to do ground radials next summer. It will be an interesting comparison.
I must apologize for not mentioning in my earlier post that the idea of using a pair of 1/4 wl 75
ohm feedlines in parallel was something I read by Tom, W8JI.
The line impedence of two paralleled 1/4 wl 75 ohm lines is 37.5 ohms, which inverts to 56.25 ohms
at the transmitter end and provides a 1.13 :1 match to 50 ohms. Does the line impedence of 37.5 ohms
also invert to 56.25 ohms for other odd multiples of 1/4 wl...i.e., 3/4 wl, 5/4, etc....???
Also, would such a transmission line transformer arrangement benefit from coiling the extra doubled
coax into a choke at the feedpoint? If so, how many turns/diameter would make it effective?
Last, I have a spool of RG59/U CATV coax with stranded center conductor and double shield.....tinned
braid plus a foil under the braid that seems like it's glued onto the soft white dialectric. It's
marked "Omnicable P/N E15901 RG59/U E82833 20 AWG 75*C (UL) Type CL2 OR CATV". Will this stuff do
the job? How much power will a paralled pair handle? And what would be its Velocity Factor?
73, Jerry K3BZ
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